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Re: Have you ever noticed

Erin and my husband would get along He has used our kitchen scale for his own home "experiments" on many occasions.

The temperature difference between 40F milk and 70F milk would make negligible difference in density. I am an engineer and we round everything, but the scientist started that trend by making the assumption that we could reasonably use the properties of water. My kitchen scale only gets down to the 1/8th of an ounce anyway.

ETA: maybe if I could read I would have seen this was already pointed out!

Re: Have you ever noticed

Originally Posted by @llli*sassypants

Erin and my husband would get along He has used our kitchen scale for his own home "experiments" on many occasions.

The temperature difference between 40F milk and 70F milk would make negligible difference in density. I am an engineer and we round everything, but the scientist started that trend by making the assumption that we could reasonably use the properties of water. My kitchen scale only gets down to the 1/8th of an ounce anyway.

ETA: maybe if I could read I would have seen this was already pointed out!

I think we posted at the same time, so it was more an issue of the fact that we weren't taking turns.

Re: Have you ever noticed

Originally Posted by @llli*scienceteachermommy

The difference in density in water from 30 C and 0 C is less than 1%, which, I would expect, is less than the error inherent in a kitchen scale. When I have done this as a lab experiment, both as a student and as a teacher, the students have looked up the density of water at the temperature of the room.

The difference in density with temperature is definitely smaller than the error in filling the bottles.

You're totally right. It had just occurred to me that a kitchen scale is not nearly precise enough to pick up on that small of a difference. Even on a triple beam, when I've done density labs the range in my students measurements of the density of water is pretty large. Although some of that my have to do with their inability to properly zero a scale.

Re: Have you ever noticed

Originally Posted by @llli*phi

You're totally right. It had just occurred to me that a kitchen scale is not nearly precise enough to pick up on that small of a difference. Even on a triple beam, when I've done density labs the range in my students measurements of the density is pretty large. Although some of that my have to do with their inability to properly zero a scale.

Re: Have you ever noticed

Pedagogically speaking, the students waste so much time trying to get an accurate weight or don't get an accurate weight, that the point of the lab is often lost.

In chemistry the push to teach more and more microscale, or at least miniscale, makes triple beams almost useless. My 9th graders could probably weigh better by guessing.

ETA: STOP DISTRACTING ME FROM GRADING, YOU EVIL PEOPLE! (And I mean that in the kindest, most attachmenty sort of way.)

The only course I use a scale for is my history of life class and that's only for one lab, but we've never really had any problems. Now that I think of it though I've almost always used triple beam balances as an undergrad and as a TA over way too many years of grad school, so it's not just me out there using old equipment (but I didn't take an excessive number of chem courses either). However, I think our goals are significantly different given our fields. I'm not teaching stoichiometry or anything like that where it is going to matter much if their measurements are off. All I need them to do is estimate some bulk compositions and infer mechanisms from their estimates. It's the illustration of the mechanisms that matters to me, not the measurements themselves.

And I'm procrastinating grading finals myself. I bet I hate grading more than you hate triple beam balances. Every year there is a small part of me that wants to ditch essay questions for multiple choice, but I'll never be able to actually do it. Okay, I'll go now...

Re: Have you ever noticed

Originally Posted by @llli*phi

I bet I hate grading more than you hate triple beam balances. Every year there is a small part of me that wants to ditch essay questions for multiple choice, but I'll never be able to actually do it. Okay, I'll go now...